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Description
The Los Alamos Neutron Science Center uses a room temperature coupled-cavity linac to accelerate H- ions from 100 to 800 MeV. It is powered by forty-four 1.25 MW peak 805 MHz klystrons, each capable of 150 kW of average power. A prototype solid-state amplifier (SSA) feasibility study began in 2024, as reported at 13th CWRF Workshop in Oak Ridge. We are using high voltage Gallium Nitride (GaN) on Silicon Carbide (SiC) high electron mobility transistors to reduce the number of active devices and the complexity of power combing smaller amplifiers. These wide bandgap semiconductors can operate at high channel temperatures around 200 degC without shortened life. We are testing devices up 5 kW of peak power at 100 volts. Operating in saturation mode, outphasing modulation between pairs of amplifiers is used to maintain high device efficiency to reduce thermal dissipation, compared to conventional class AB linear amplifiers. The power supply requires stored energy with a capacitor bank. Power combining uses a combination of 2-way Gysel, 40-way radial and magic tee combiners in waveguide. Combiner testing has been underway. Cooling design is critical for such as high power-density amplifier. A new test lab is testing HEMT pallets, power supply/energy storage, and passive RF components for a medium power prototype. We have determined that a SSA can replace a klystron, while fitting within the existing footprint to use the same water-cooling plant.